<topic>
	<head>
		<title>ACOS</title>
		<keywords>
			<keyword term="functions, ACOS" />
			<keyword term="mathematical functions, ACOS" />
			<keyword term="ACOS function" />
		</keywords>
		<links>
			<link href="Functions.html">Functions</link>
			<link href="Mathematical Functions.html">Mathematical Functions</link>
		</links>
	</head>
	<body>
		<summary>
			<p>
				A mathematical function that returns the angle, in radians, whose cosine is the specified double expression; also called arccosine.
			</p>
		</summary>

		<syntax>
			<code xml:space="preserve">ACOS(value AS double) RETURNS double</code>
		</syntax>

		<parameters>
			<params>
				<param name="value">
					<p>
						A number representing a cosine, where <c>-1 ≤ value ≤ 1</c>.
					</p>
				</param>
			</params>
		</parameters>

		<returns>
			<p>
				An angle, θ, measured in radians, such that <c>0 ≤ θ ≤ π</c>
			</p>
			<p>
				-or-
			</p>
			<p>
				<c>NaN</c> if <c>value &lt; -1</c> or <c>value &gt; 1</c>.
			</p>
		</returns>

		<examples>
			<sampleCode language="NQuery.SQL" xml:space="preserve">SELECT 'The ACOS of the angle -1 is: ' + TO_STRING(ACOS(-1)) AS Result</sampleCode>
		</examples>
	</body>
</topic>
